1. Field of the Invention
The present invention generally relates to manufacturing methods of semiconductor devices, and more particularly, to a manufacturing method of a semiconductor device that includes a step of sealing the semiconductor device by providing a sealing member on a substrate mounting a semiconductor element thereon.
2. Description of the Related Art
Recently, with the rapid progress and development in information communication technologies, improvement of data communication speed and increase in data communication amount have been realized, and mobile electronic devices such as mobile phones and notebook computers incorporating therein a semiconductor device (imaging apparatus) such as a CCD (charge coupled device) image sensor and a CMOS image sensor are becoming popular. Such mobile electronic devices can transmit in real time image data obtained by an imaging apparatus in addition to character data (refer to Japanese Laid-Open Patent Application No. 2002-185827, for example).
FIG. 1A shows such a conventional imaging apparatus 100. As shown in FIG. 1A, the imaging apparatus 100 generally includes an optical sensor element 1, a substrate 2, and a holder 5. The optical sensor element 1 is, for example, a CCD image sensor or a CMOS image sensor. The optical sensor element 1 is mounted on the substrate 2.
The holder 5 is provided with a lens 6 for focusing an image on a photo-accepting surface of the optical sensor element 1. The holder 5 is fixed to the substrate 2 by using adhesive 4. Thus, the optical sensor element 1 is sealed in an internal space 7 formed in the holder 5. Accordingly, it is possible to prevent dust from adhering to an imaging surface of the optical sensor element 1.
Referring to FIGS. 1A and 2A through 2C, a description is given below of a manufacturing method of the imaging apparatus 100 having the above-mentioned structure.
In order to manufacture the imaging apparatus 100 shown in FIG. 1A, first, as shown in FIG. 2A, the optical sensor element 1 is mounted on the substrate 2. Although not shown in the drawings, the optical sensor element 1 is electrically connected to the substrate 2 by, for example, gold wire.
Then, as shown in FIG. 2B, the adhesive 4 is deposited on a top surface of the substrate 2 at a predetermined portion by using a dispenser 3. The positions at which the adhesive 4 is deposited are set so as to correspond to the shape of a bottom end of the holder 5. Generally, a thermo-setting resin, which provides a good bonding and achieves reliable bonding, is used as the adhesive 4.
Upon completion of the depositing process of the adhesive 4, as shown in FIG. 2C, the holder 5 is pressed against the substrate 2 at the positions where the adhesive 4 is deposited so as to temporarily fix the holder 5 to the substrate 2. Then, the substrate 2 on which the holder 5 is temporarily fixed is loaded in a curing apparatus and a curing process (heating process) is performed so as to cure the adhesive 4. Consequently, the adhesive 4 is cured and the holder 5 is bonded to the substrate 2.
With the above-mentioned manufacturing steps, the imaging apparatus 100 as shown in FIG. 1A is manufactured. Since the optical sensor element 1 is sealed by the holder 5 as mentioned above, it is possible to prevent dust or the like from adhering to the optical sensor element 1.
In a state where the holder 5 is temporarily fixed to the substrate 4 by using the adhesive 4, the internal space 7 formed between the substrate 2 and the holder 5 is airtight. When the curing process is performed in such a state, the air in the internal space 7 is heated and expanded, which results in an increase in the air pressure in the internal space 7. Thus, a difference (air pressure difference) is generated between the inside and outside of the holder 5.
As mentioned above, in the manufacturing method of the conventional semiconductor device, the curing process is performed in the state where the internal space 7, which is formed by the holder 5 and the substrate 2, is sealed. Hence, as shown in FIG. 1B, there is a problem in that a damaged portion 8 may be generated at a bonding position between the substrate 2 and the holder 5 due to the increase in the air pressure in the holder 5 (internal space 7), and airtightness of the internal space 7 formed by the holder 5 and the substrate 2 may not be maintained even if the adhesive 4 is cured. In such a case, dust may enter the internal space 7 via the damaged portion 8 and adhere to the optical sensor element 1, which causes a reduction in reliability of the imaging apparatus 100.